Advances have been made in techniques and tools for use in minimally invasive surgery that can be performed through small incisions or intravascularly. For example, improvements have been made recently to reduce the invasiveness of cardiac surgery. To avoid open procedures, such as open, stopped-heart surgery, which can lead to high patient morbidity and mortality, devices and methods have been developed for operating through small incision, for operating on a beating heart, and for performing cardiac procedures via intravascular or intravascular access. For many minimally invasive surgery techniques, significant challenges include positioning the treatment device or devices in a desired location for performing the procedure and deploying the treatment into or on the target tissue.
Heart valve repair can benefit from less invasive surgical techniques. Traditional treatment of heart valve stenosis or regurgitation, such as mitral or tricuspic regurgitation, typically involves an open-heart surgical procedure to replace or repair the valve. Valve repair procedures usually involve annuloplasty, which is a set of techniques designed to restore the valve annulus shape and strengthen the annulus. Conventional annuloplasty surgery generally requires a thoracotomy (a large incision into a patient's thorax), and sometimes a median stemotomy (an incision through a patient's sternum). These open-heart, open-chest procedures routinely involve placing the patient on a heart-lung bypass machine for long periods of time so that the patient's heart and lungs can be stopped during the procedure. In addition, valve repair and replacement is typically technically challenging and requires a substantial incision through a heart wall to access the valve. Many patients such as elderly patients, children, patients with complicating conditions such as comorbid medical conditions or those having undergone other surgical procedures, and patients with heart failure, are not considered candidates for heart valve surgery because of the high risk involved.
Minimally invasive procedures are typically performed endoscopically through catheters, through small incisions or intravascularly. Instruments such as graspers, dissectors, clip appliers, lasers, cauterization devices and clamps are routinely used endoscopically, with an endoscope used for visualizing the procedure. When a surgeon desires to bring pieces of two tissue together, the surgeon typically threads a suture through the two pieces of tissue, applies tension, and ties off or knots the suture to maintain the tension. However, during endoscopic surgery, the manipulation required when knotting or tying suture material can be difficult because of severely restricted space.
Previously, there have been attempts to maintain tension in tissue by using staples, clips, clamps, or other fasteners to obviate the need for suturing. However, these methods do not provide adjustable tension such as is available when a surgeon uses suture. U.S. Pat. Nos. 5,520,702 and 5,643,289 describe deformable cylindrical tubes that can be applied over a loop of suture. After a suture is adjusted to a desired tension, the suture is looped, and a deployment gun applies a deformable tube over the suture loop and crimps it so that it clamps down on the suture. After the loop is secured with a crimp, a separate cutting member or tool can be used to cut the excess suture material. U.S. Pat. No. 6,099,553 also describes deformable crimps that can be applied over the ends of sutures to fix them into place. Similar crimping devices that operate to mechanically fasten suture together and cut away excess tether are provided as TI-KNOT® knot replacement systems by LSI Solutions.® However, with crimping schemes, the suture may still slip through crimps and lose tension, especially if the suture has a small diameter, if the suture is made of a material susceptible to slippage, such as metal or TEFLON® fluoropolymer, or if the crimp is insufficiently deformed. U.S. Publication No. 2003/0167071 describes fasteners made from shape memory materials that can be applied to sutures to avoid tying knots in catheter-based procedures. U.S. Pat. Nos. 6,409,743 and 6,423,088 describe fusible collars that can be used in place of knots in securing sutures. These fusible collars require an external source of energy be locally applied to the collar without damaging surrounding tissue for the fusing process.
Devices and methods for less-invasive repair of cardiac valves have been described. In heart valve repair procedures, it is often desired for a physician to secure one or more treatment devices to valve annulus tissue. Annular tissue tends to be more fibrous than muscular or valve leaflet tissue, and thus can be more suitable tissue for securing treatment devices such as anchors to treat a heart valve. Devices and methods for positioning anchor delivery devices are described in U.S. Patent Application Ser. Nos. 60/445,890, 60/459,735, 60/462,502, 60/524,922, 10/461,043, 10/656,797, 10/741,130 and 10/792,681, which were previously incorporated by reference. For example, these references describe devices and methods for exposing, stabilizing and/or performing a procedure on a heart valve annulus.
Many treatments, including annuloplasty, involve tightening of tissue. For some tissue tightening procedures, anchors coupled to a suture are embedded in tissue, and the suture is then cinched to tighten the tissue via the anchors. Examples of devices and methods for such procedures applied to heart valve repair are provided in U.S. patent application Ser. Nos. 10/656,797, 10/741,130 and 10/792,681.
Improved methods and devices for locking a suture to maintain tension in the suture are desired, especially in minimally invasive treatments where surgical access is limited. For treatments involving tissue anchors, improved methods and devices are desired for locking a suture that has been coupled with the anchors such that the suture does not move relative to the last applied anchor. Also desired are improved methods and devices for severing excess suture so that it can be removed.